Fix empty class dropdown on Attendance for admins

The classes query filtered by teacher_id when isAdmin was momentarily false
(roles not yet loaded) and never refetched — cache key lacked isAdmin. Gate on
!loading and include isAdmin in the query key.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/routes/_authenticated/attendance.tsx

@@ -14,20 +14,22 @@ export const Route = createFileRoute("/_authenticated/attendance")({
 });
 
 function AttendancePage() {
-  const { user, roles } = useAuth();
+  const { user, roles, loading } = useAuth();
   const isAdmin = roles.includes("admin");
   const qc = useQueryClient();
   const [date, setDate] = useState(new Date().toISOString().slice(0, 10));
   const [classId, setClassId] = useState<string>("");
 
   const { data: classes } = useQuery({
-    queryKey: ["my-classes", user?.id],
+    // isAdmin is in the key so the query refetches once roles resolve; gated on
+    // !loading so it never runs with a not-yet-known (false) admin status.
+    queryKey: ["my-classes", user?.id, isAdmin],
     queryFn: async () => {
       let q = supabase.from("classes").select("id, name, teacher_id");
       if (!isAdmin) q = q.eq("teacher_id", user!.id);
       return (await q.order("name")).data ?? [];
     },
-    enabled: !!user,
+    enabled: !!user && !loading,
   });
 
   const { data: students } = useQuery({